The present invention relates to networks for connecting peripheral devices such as memory and printers to one of a plurality of computers.
With the rising popularity of small home computers it has become desirable to tie computers into a simple network for various purpose, e.g. for teaching computer operating principles in a classroom setting. Under such circumstances it is desirable to enable a plurality of small computers to use a commmon printer and disk drive. This common usage can dramatically decrease cost and improve the reliability of the system. It is also desirable under such circumstances to enable an instructor to gain control of the printer and disk drive or to monitor the video output from a particular student while giving him audible instructions.
It is known, (for example, U.S. Pat. No. 3,881,174) to use a central computer which may address a plurality of peripherals. A disadvantage with these known systems is the requirement that a peripheral must request an interrupt and then await an interrupt acknowledge. These systems are complicated because the connections may occur randomly which requires a form of two-way communication between a central and peripheral devices. A complicated decision must be made as to which connection will be made first either due to some predetermined hierarchy or due to an early request.
It is also known to employ teaching systems having a teacher console for receiving responses to questions manually entered by students at their separate stations. However, these systems are not concerned with the data processing considerations necessary to allow a common peripheral such as a disk drive or printer to service a plurality of computers. Time division multi-plexing is also known as a technique wherein a predetermined time slot is allotted to one of various signal sources. However, these systems do not permit one source to stop the multi-plexing and use the communications lines continuously.
Accordingly, there is a need for an improved computer network system which will allow the linking together of the foregoing equipment.